Paclitaxel (taxol), represented by the following structural formula: ##STR1##
is a potent antitumor compound. Paclitaxel exhibits a unique mechanism for preventing the growth of cancer cells by affecting the microtubules, which play an important role in cell division and other cell functions. At the beginning of cell division, a large number of microtubules are produced, and as the division reaches an end, the microtubules are normally broken down. Taxol prevents microtubules from breaking down, which has the effect of clogging up cancer cells to an extent that the cells cease to grow and divide.
Taxol is clinically effective for the treatment of refractory human ovarian and breast cancer, and has exhibit promising activity against a number of other types of cancers such as liver, peritoneal, cervical, prostate, colon, and esophageal cancers.
Taxol was primarily extracted from the bark of the Pacific yew Taxus brevifolia. Unfortunately, the yew grows very slow, approximately eight inches per year, and therefore the tree is a limited source of taxol. This has lead researchers to seek alternative means for producing taxol and analogs thereof which may display superior antitumor activity.